The Global Financial Crisis started in the summer of 2007 in the US.
The demand on real estates in the US was growing since 2004 and therefore the price of those did grow too.
A lot of people raised credits to buy new real estates as their value was increasing all the time.
That was up to 2006 when the value of those estates started to drop. So the banks wanted their debtors to provide more financial securities which they couldn't do.
Therefore the banks took the real estates back which had lost greatly in value up to that time. This led to the banks sitting on their real properties which no one wanted to buy.
As the banks needed money they raised credits oversea which led to the international aspect of the crisis where we find ourselves in now.
